This invention relates to a device for holding a workpiece firmly on a work table by means of a vacuum, and more particularly to a vacuum cell device which may be adjusted in its horizontal position on the table as well as its vertical position above the table for holding a wide variety of workpiece shapes and sizes on the same work surface.
Heretofore, vacuum hold down devices have been provided for holding various materials in many different types of industrial machinery operations without the use of clamps. One particular type of vacuum hold down system includes the use of a "spoil board" which is made in the image of the part to be machined or produced. The spoil board is lined with a gasket material so that vacuum can be applied to the central part of the board to hold the blank workpiece for machining. However, this system requires a different "spoil board" for every size and shape of workpiece that is to be machined. The resulting set up times to change from one workpiece to the next makes the system relatively inefficient.
Another system commonly used in the trade is referred to as the vacuum-pod system. The vacuum-pod system requires a large board which has been drilled and fitted with hundreds of vacuum-pods arranged so that in any situation the required vacuum-pods can be activated by inverting the pod to cause vacuum to flow through the pod and hold the workpiece or part in that particular location. This system requires the purchase of hundreds of vacuum-pods, the provision of a large number of vacuum-pod locations, and does not provide for vertical adjustment of the vacuum-pods or workpieces. In many manufacturing or machining operations, the workpieces have uneven surfaces. Because of this, and other reasons, it is highly desirable to be able to adjust the vertical height of the device or unit which is holding the workpiece so that the top surface which is being machined or worked on may be presented in a planar position. Further, the work table surface on which the workpieces are supported are not always perfectly level and require vertical adjustment for the planer positioning of a workpiece. To be able to accommodate different sizes and shapes of workpieces, it is desirable to be able to vary the number of devices utilized to support the workpieces without undue difficulty and expense.
Various individual workpiece holders have been provided for holding different types of workpieces and small parts. In particular, small part holders have been utilized in the semi-conductor field to hold small circuit and other electronic elements for processing such as shown in U.S. Patent Nos. 3,520,055; 4,403,567; 4,596,569; and 3,475,097. These devices are usually suitable only for miniature parts. For this purpose, the workpiece holders typically include small orifices through which a vacuum is drawn for holding the miniature workpiece. U.S. Pat. No. 3,484,093 discloses an article holding apparatus wherein a miniature workpiece is supported on resilient rings projecting above a surface through which a vacuum admission hole communicates. None of the small part, workpiece holders are suitable for holding large workpieces which are processed in industrial machining and manufacturing operations.
Accordingly, an object of the invention is to provide an improved workpiece holding device of the vacuum type for supporting a variety of workpiece sizes and shapes.
Accordingly, an object of the invention is to provide a workpiece holding device of the vacuum type which may be adjusted horizontally and vertically relative to a work surface in a quick and convenient manner.
Another object of the present invention is to provide a vacuum workpiece holding system comprising a plurality of individual workpiece which may be adjusted in their position relative to a work table surface in order to be optimally located for supporting a specific workpiece shape and size in a proper position.
Still another important object of the present invention is to provide a vacuum workpiece holding system comprising a plurality of individual vacuum cells which may be adjusted in their vertical position relative to a workpiece table to support a workpiece in a level, planar configuration.